1. Field of the Invention
This invention pertains to elevated cableway systems used in mass transit systems and the like, and, more particularly, to an improved cableway for such systems.
2. Description of the Prior Art
Many types of elevated cableway systems have been used in or proposed for mass transit systems. One such system is disclosed and claimed in U.S. Pat. No. 4,069,765 issued Jan. 24, 1978 to Gerhard Muller. This system is neither a suspension, or cable stayed bridge nor an aerial tramway. Consequently, not all standard design criteria are necessarily applicable to the system in the Muller '765 patent.
Thus the Muller '765 patent discloses a non-standard approach and FIGS. 1-5 of the present application correspond to FIGS. 3-7 of the Muller '765 patent. FIG. 1 illustrates in gross an elevated cableway system 10 in which vehicle 12 travels along track cable systems 14 suspended from catenary, or support cable 16. As shown in FIGS. 2-3 and 5, track cable systems 14 comprises locked-coil steel cables 14a-d and catenary cable system 16 comprises locked-coil steel cables 16a-b. Returning to FIG. 1, a plurality of pylons 18 elevate and support track cable systems 14 and catenary cable system 16 between the termini 20 of system 10. Track cable systems 14 and catenary cable system 16 are preferably anchored to ground 19 to sustain horizontal cable forces and transmit them to ground 19.
One of Muller's basic approaches is illustrated in FIGS. 1-2. Stress loads associated with the "sag" in track cable systems 14 and catenary cable system 16 caused by the weight of vehicle 12 were a problem for cableway systems at the time Muller filed the '765 patent application as shown in FIG. 1. Muller proposed, as disclosed in the '765 patent, to address these problems by pre-tensioning, or pre-stressing, track cable systems 14 so that track cable systems 14 levelled under the weight of vehicle 12 as shown in FIG. 1.
Part of Muller's proposed design included new cross-ties 15 and hangers, or spacers, 7 for suspending track cable systems 14 from catenary cable system 16. These cross-ties 15 and hangers 7, which were new at the time, are illustrated in FIGS. 2-3. Through this suspension system, track cable systems 14 were tensioned as described above and, consequently, "bowed" upward when not weighted by vehicle 12. This approach has worked well and is incorporated in the present invention as set forth below.
Muller also proposed tying track cable systems 14 and catenary cable system 16 together between pylons 18 at points 22 as shown in FIG. 4. Muller tied the cables with force equalization plate 24, in cooperation with clamping plate 26 and wedges 28. Force equalization plate 24 also improved the distribution of load stresses in the cableway system and, in combination with tensioning track cable systems 14, substantially advanced the art.
Muller also adopted the pylon structure earlier disclosed in U.S. Pat. No. 3,753,406. As set forth in column 1, line 65 to column 2, line 3 of the '765 patent, it was thought the pylons in such a system must be "stiff". It was though that "self-aligning" or "self-adjusting" pylons would introduce undesirable longitudinal shifting between the catenary and track cables. However, we now know that "self-aligning" or "self-adjusting" pylons produce substantial design benefits provided measures are taken to minimize or eliminate longitudinal shifting.
Some problems also appeared in implementing Muller's design despite its great advance over the art. For instance:
(1) catenary cable system 16 was strung over rollers on the top of pylons 18 and began to wear from the movement across the rollers as vehicle 12 traversed the cableway;
(2) the design of the equalizer plate 24 could also cause problems by kinking cable elements 16a-b, and 14a-d, under some circumstances; and
(3) cable elements 14a-d were required to have upper surfaces engageable by the wheels of the vehicle because the equalizer plate did not provide for such engagement.
It further came to be realized that load stresses could be better distributed through redesign of the force equalizing assembly as well as the hangers and cross-ties, particularly in light of the new pylon designs.
U.S. Pat. No. 4,264,996 by Baltensperger and Pfister describes a suspended railway system with towers that support a catenary cable atop the towers and support track cables with a "stressing beam" that is pivotally connected to the towers. The '996 system is, however, distinguishably less capable than the present invention. For instance, the '996 patent fails to grasp the catenary cable at the support on top of the tower. Therefore, as described in the 1996 patent, the cable is allowed to slip in the notches of the support. This slippage will inevitably cause wear on the cables.
Additionally, while the stressing beam gives some measure of weight redistribution at the track cable support, the fact that there is only one beam and the fact that the beam merely pivots about a single point ensures that the impact with the support of a vehicle passing over the support will not be substantially lessened. When weight is applied to one end of the beam, the other end of the beam necessarily must tilt upwardly thereby creating a ramp for a vehicle traversing the track to climb. With only a single beam, the tilt of the beam cannot be lessened until the vehicle passes each point along the beam. If the beam had secondary and tertiary beams connected to it as the present invention does, the moment about the central pivot point could be lessened in advance of the vehicle. With secondary and tertiary beams, the point of applied load is the point where the secondary beam attaches to the main beam, not the point the vehicle is passing.
It is therefore a feature of this invention that it provides an improved pylon design for elevated cableway systems.
It is furthermore a feature of this invention that the improved pylon design reduces wear on the catenary cable system by not allowing the catenary cable system to slide or role directly on the top of the pylon.
It is furthermore a feature of this invention that the improved pylon includes a new, deflecting upper saddle to support the catenary cable system while relieving stresses imposed on the catenary cable system by deflecting under load applied by the vehicle traversing the track cable system.
It is a still further feature of this invention that the improved pylon includes an improved, pivotable lower saddle to better transmit forces and distribute load stresses through the cableway system as the vehicle traverses the cableway.
It is furthermore a feature of this invention that load stresses are distributed through improved hanger and spacer designs.
It is still furthermore a feature of this invention that it provides an improved cableway system with greater lateral support for the union between the catenary and track cable systems by providing improved force equalizing assemblies.
It is still furthermore a feature of this invention that it provides an alternate force equalizing assembly that reduces wear on the catenary cable system and the track cable systems by allowing the cables to controllably yield relative to one another as force is transferred between them.